Please see links below for global SST details. The largest expanse of warmest ocean waters globally persist across the equatorial and North Indian Ocean, with totals in excess of 30C and anomalies ~plus 1-2C. As is typical prior to monsoon onset, the 30C SST isotherm has been expanding northward into both the Bay of Bengal and Arabian Sea. There has also been warming of the equatorial west central Pacific Ocean, with totals ~30C and roughly plus 1C anomalies.

In general, slightly positive SST anomalies cover the equatorial Pacific Ocean basin and the slope of the thermocline continues to decrease. Anomalous surface westerly wind flows linked to the ongoing MJO has contributed to this evolution. However, for numerous reasons the ENSO situation is unclear and diligent monitoring must continue. For example, if coherent dynamics start to “heat” the equatorial west Pacific substantially during boreal summer into autumn, then I will get impressed about the possibility of transitioning to a warm event. Regardless, subseasonal activity (GWO/MJO, etc.) will continue, and these will impact North America.

While the general behavior of our weather-climate situation continues to evolve as expected during the past several weeks, many details have become more complicated than I would like. I do think I see “what is going on”; however, I have typed that before and drawn the wrath of Rex the Rottweiler! Somewhat analogous to rolling a backup bowling ball and relying on that to get a Brooklyn strike, I feel my poor USA assessment a week ago for this upcoming week (western USA trough for a period of days) was partly linked to “playing the MJO card” while not being conscientious enough about its initiation. That is, stochastic GWO dynamics forced its initiation during early-mid March around Indonesia (see past discussions), and that forcing appears to have been “taketh away”. This once again demonstrates to me and should also to the rest of the world that it is important to keep in mind the on-going dynamics, and to know better than “play a signal” regardless of its origins (for example). The latter are serious basic research issues, and there is no way I can do justice about those matters here.

WH (2004) plots updated through 7 May show a greater than 1 sigma projection in octant 7 (west Pacific Ocean) of phase space, having done a loop from a week ago. I was expecting phase 8 then 1. In reality, there is no “loop” in the atmosphere. The trace is an artifact of this empirical technique. Animations of upper tropospheric daily mean vector wind anomalies show a well-defined subtropical wave train (SWT) propagating through the Eastern Hemisphere ~30N forced by interactions with the extratropics (sound familiar?). That has disrupted the MJO signal, and the dynamics do involve the WB (2009) measure of the GWO. For example, tied to the SWT (a zonally oriented RWD typical of a GWO response), anomalous upper tropospheric twin anticyclones are returning to Africa and the western Indian Ocean. In other words, and consistent with the past 2008-09 boreal cold season, I offer that the GWO is again driving the MJO. It is clear to me that the extratropics are currently forcing the tropics. Could this kind of behavior be telling us something about where ENSO is going?

Full disk satellite imagery and other tools show that the global signal of tropical convective forcing is somewhat disorganized. However, cutting to the chase, the African Highlands/Gulf of Guinea regions are active, there is Indian Ocean “sputtering” and a convectively coupled Rossby mode is over western Indonesia. It is probable there will be some form of consolidation over much of the Indian Ocean during the next 1-2 weeks. The west Pacific Ocean (loosely) is also somewhat active, and that region may again become a “wild card” UFN (recall our "nemesis"). During weeks 2-3, enhanced rainfall should further consolidate/shift into the region of Indonesia, and the Eastern Hemisphere monsoon systems may also be active at that time. It is uncertain whether or not a “REAL” MJO will initiate during the next several weeks.

As expected, the GWO projection in phase space is improving located in octants 8-1 through 7 May. It is at this point where I can only “hope” readers can start to put things together (need maps!). Tied to the SWT interacting with the MJO signal, etc., a strong negative global friction-clustered mountain torque index cycle is in progress as I type. The latter is contributing to a decent negative global AAM tendency (~20 Hadleys relative to R1 data climatology) with much of the zonal mean contribution coming from the subtropical atmospheres. Stated another way, several circulation features characteristic of La-Nina are returning. A response is that our strong North Pacific Ocean jet is collapsing, one of the reasons all numerical models have been performing poorly (along with me!) for about the past week. Other behaviors include above average easterly wind flows increasing ~25-30N/35S, zonal mean storm tracks shifting anomalously poleward at least across the Northern Hemisphere, and ridges starting to dominate the extratropics.

Summing up so far, could our “May surprise” be a re-emergence of stationary tropical forcing across the Eastern Hemisphere favoring an eventual return to La-Nina? Or, will we finally see the initiation of decent coherent MJOs that could significantly impact the equatorial Pacific? These are only 2 of an infinite number monitoring issues, and stay tuned. I wanted to make a bit of an effort to get readers to gain an even better appreciation of some of the serious real-time scientific matters that are currently (and always) involved spanning wide time and space scales. This is an example of the next level of weather-climate research/monitoring that is needed, and hopefully that will come to fruition via the ESRL/PSD GSDM web page.

As I typed last week, a GWO/MJO 8-1-2 transition is in progress (WH “loop” understood). The 250mb GWO snr psi composite anomaly plot for phase 1 reasonably depicts the current global circulation. One can also argue a loose superposition of MJO phases 1-2 with GWO phase 1. Per above, with reasonable confidence (I hope!), I offer that a superposition of phases 2-3 for both the GWO and MJO 250mb snr plots for psi and other variables is plausible through at least week-2. For the USA, this suggests our familiar synoptic pattern of progressive western and central states troughs increasing the risk of severe local storms across the central and northern Plains/Upper Mississippi Valley. Possible weather globally can also be inferred from the composites, in addition to the expertise of the international centers. There has been some recent increase of global high impact weather.

Afterward, and I think some readers will understand why, I do have some concern (low confidence) that heading into June, with perhaps many episodes through August, that a synoptic pattern typical of ~GWO phase 4 may occur. That is, per 250mb snr psi composite anomaly plots centered ~15 July, USA west and east coast ridges with troughs across the central states into the Great Lakes at times are possible. While there may be periods of cool and wet for the Plains and Great Lakes states, episodes of intense heat may occur particularly west of the Continental Divide.

Appendix

All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We are working to mainstream this effort. The support is very much appreciated!

Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):

These are probabilistic statements. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.

The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), is (still) awaiting publication in MWR. An early on-line release can be downloaded from the following link:

In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a complete subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook, extremely unscientific, and makes Rex the Rottweiler VERY angry! I am planning on posting a discussion next weekend, 15-17 May.

5 comments:

Great job, as usual, Ed. I think everyone can agree that the models have provided headaches for a lot of folks out there...

I live in southern MB...and, we got our first thunder of the season on Wednesday. I'm excited for the upcoming season....

2 strong low pressure systems look to be heading my way....one on Tuesday/Wednesday...and, the other at the start of the May Long weekend. I'm not expecting anything severe yet...but, some elevated convection looks good right about now...

Do you see this pattern continuing? It seems that the upcoming lows will be quite far north for this time of the year (southern prairies). The way you worded your blog towards the end, it looks like I could be dealing with a lot of MCS and MCC's this summer....

As I discussed, uncertainty is about as bad as it gets. La-Nina characteristics (should that be the case) do suggest the storm track to be shifted north. Depending on those unclear synoptic details, this upcoming summer may be favorable for MCS activity particularly ~July-mid August.

However, if ridges start to dominate western North America, you may be relatively cool/dry. The latter is a possibility I am concerned about. We will see.